1. Field of the Invention
The present invention relates generally to the field of psychotic disorders, such as schizophrenia and bipolar disorders. More particularly, it concerns genetic markers of antipsychotic response, for example, genes and genetic markers that influence or predict a person's likely response to antipsychotic medications.
2. Description of Related Art
Numerous drugs exist to treat psychotic disorders, such as schizophrenia (SZ), related SZ-spectrum disorders (including schizotypal personality disorder (SPD) and schizoaffective disorder (SD)), and bipolar disorders (BD). Most of these drugs fall into one of two categories, typical (first generation) and atypical (second generation).
Although head to head studies of large groups of patients, either in the acute phase or outpatient treatment, show that most atypical antipsychotic drugs are equally efficacious for positive symptoms, there are individual differences in response to specific drugs based on differences in drug pharmacology and metabolism, combined with genetic differences between patients. There are currently no proven ways to identify which antipsychotic drug is optimal for a given patient. Thus, patients switch from one drug to another when response is not considered to be adequate or side effects are intolerable. This switching of medication incurs a variety of increased costs, both economic and patient and caregiver hardship. On average, each patient may change medications three times before finding one that works. Additionally, the current drugs have significant side-effects. This combination of side-effects and limited efficacy create a vast unmet need for selecting the optimal antipsychotic for each patient.
Moreover, the limited or partial response that is often seen with antipsychotics leads to polypharmacy, where physicians prescribe two or more antipsychotic drugs plus mood stabilizers and/or antidepressants. Polypharmacy increases medication costs and significantly increases the likelihood of adverse advents and drug interactions (Stahl and Grady, 2006).
Pharmacogenomics, using genetic variation to predict altered response and side-effects profiles, will be important for enhanced patient care going forward. There continues to exist, therefore, a need to identify specific genetic variations that are associated with treatment outcomes for psychotic disorders.